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Fade on, Fade off Interior lights


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KPierson 
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Posted: October 30, 2006 at 7:58 AM / IP Logged  

No, because the cap is in parallel with the light (resistor).  When power is applied the bulb will pull X amount of current and the cap will pull Y amount until fully charged.  The light will pull X amount regardless if the cap is there or not.

But, when power is removed the circuit changes (From a parallel circuit to a circuit in which the cap is the battery), and the cap becomes the power source.  As the voltage drains in the cap the light will dim.

I haven't tested this at all, but that is what I would guess would happen.  I may be wrong.

Kevin Pierson
kymadan 
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Posted: October 30, 2006 at 8:41 AM / IP Logged  
Sounds like it makes sense..... Does anyone know how to figure out how long it will stay on for?
KPierson 
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Posted: October 30, 2006 at 11:53 AM / IP Logged  

Time = RxC

C is the capacitance of your cap, R is the resistance of your bulb.  That should give you an approximation.

According to the information you provided the resistance of your bulb is ~14.4 ohms.  Your capacitance is 22000uF.

This would give you a time basis of 316800uS, or .316 seconds.  For a 1 second delay I would figure on using a 68000uF cap.

Kevin Pierson
kymadan 
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Posted: October 30, 2006 at 12:12 PM / IP Logged  
So if I used a  220,000 uf cap, and with the light being 14.4 Ohms, I would take 220,000 X 14.4 =  3,168,000. So that would give me 3.16 seconds?
kymadan 
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Posted: October 30, 2006 at 2:14 PM / IP Logged  

Okay, this is what I have come up with. The only problem I have is what resistor will go where the green symbol is, or even if I need one there. I believe I am going to need one that has a resistance of 14 Ohms so it will take 4 seconds to fully store, and to fully release. The plan is for it to have a delay of approximately 4 seconds after door shuts, then the relay will shut off. The 220,000 cap will then  fade until it is off in approximately 2 to 3 seconds.

Fade on, Fade off Interior lights - Page 2 -- posted image.

What do you guys think? I know I will test it before I install it, but it looks good to me. If you guys have any suggestions, please let me know. And what is your input on the "Green Resistor"

master5 
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Posted: October 30, 2006 at 2:16 PM / IP Logged  

Would the following circuit allow fade on as well? Logic tells me a cap is in a discharged state before the door is opened. Now once the door is opened a cap placed in parallel should initially shunt the circuit through the resistor  (hence no power will reach the light) and used with the light would allow a predetermined period of time before the cap charges and allows power to get to the light (with a fade I would assume determined by the "charge" rate.)

So when the door is closed and for whatever length of time decided via the timer cuts power and the discharge/rate will fade out the light. When the door is opened the above circuit should allow "fade" on if desired for whatever reason.

Am I on the right track in this thinking?

KPierson 
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Posted: October 30, 2006 at 2:32 PM / IP Logged  
kymadan wrote:

Okay, this is what I have come up with. The only problem I have is what resistor will go where the green symbol is, or even if I need one there. I believe I am going to need one that has a resistance of 14 Ohms so it will take 4 seconds to fully store, and to fully release. The plan is for it to have a delay of approximately 4 seconds after door shuts, then the relay will shut off. The 220,000 cap will then  fade until it is off in approximately 2 to 3 seconds.

Fade on, Fade off Interior lights - Page 2 -- posted image.

What do you guys think? I know I will test it before I install it, but it looks good to me. If you guys have any suggestions, please let me know. And what is your input on the "Green Resistor"

What I think will happen with this is:

Dome light signal will turn on, instantly energizing the relay, and almost instantly charging the cap (with no resistor).

As soon as the relay energizes the light will turn on, and the 220KuF cap will start to charge (light will not fade on)

Once the dome light signal is removed the 300KuF cap will keep the relay energized for a short period of time (but considerably longer then the light fade as the resistance will be about 5x greater).  Once this cap drains the relay will drop out, giving the 220KuF cap a chance to discharge in to the light, dimming it as it discharges.

I can't think of an 'easy' way to fade the light on with a cap, I would think a 555 timer or some other analog device (like mentioned in the links in the previous post) would be a better choice, but will obviously complicate everything.

Again, this is just my guess, I could be completely wrong.  Analog circuits really arn't my area of interest, I'm more of a digital guy!  :)

Kevin Pierson
master5 
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Posted: October 30, 2006 at 2:32 PM / IP Logged  

I can't help you with the green resistor value but regardless that circuit will not allow fade on. The relay is wired properly up to pin 87 which is connected directly to the light + after the cap/resistor network. The light will simply turn on via the relay instanly upon door opening. However if fade on is no longer a concern, this might work.

This circuit looks feasable to fade off but you stated earlier you also wanted a 20-30 second delay as well before fade out. This is where the timer/relay would come in handy. Once we have the RC fades straightened out (we will both need some more help with that) I can assist with a diagram to incorporate the timer delay if you desire.

master5 
Silver - Posts: 1,123
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Joined: October 10, 2006
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Posted: October 30, 2006 at 2:38 PM / IP Logged  

BTW I am not refering to any of the diagrams posted when discussing (circuit), only about my thoery of using an additional cap/resistor placed in parallel with the light to allow fade on.

As far as fade off it looks like we are getting close, just need to know if the 20-30 second delay is still being considered before fade off. 

kymadan 
Member - Posts: 39
Member spacespace
Joined: March 25, 2006
Location: United States
Posted: October 30, 2006 at 2:57 PM / IP Logged  

Well see, I decided against the 20-30 secs.... It would be a pain everytime you open the door it would stay on for that long. I decided approximately 6-7 secs is perfectly fine.

i know it will not fade on, I decided against that as well, it will come on immediately, but fade off. KPierson nailed it.

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